The reactions of indoline (I) and tetrahydroquinoline (THQ) with Os₃(CO)₁₀(CH₃CN)₂ (1) have been studied. Reaction of 1 with I at ambient temperatures gives Os₃(CO)₁₀(μ-H)(μ-η²-C₈H₇NH) (2), which decarbonylates thermally to give a mixture of the tautomeric complexes Os₃(CO)₉(μ-H)₂(μ₃-η²-C₈H₇N) (3 and 4) whose structures differ by having a μ-alkylidene−imino bonding mode (3) vs a μ-amido−aryl bonding mode (4). The conversion of 2 to 3 and 4 follows strictly first-order kinetics and the equilibrium constant K(4/3) = 6. Further thermolysis of 3 or 4 yields the dehydrogenated cluster Os₃(CO)₉(μ-H)₂(μ₃-η²-C₈H₄NH) (5). In the case of THQ reacting with 1, no direct analog of 2 is observed but a directly analogous pair of tautomers Os₃(CO)₉(μ-H)(μ₃-η²-C₉H₉N) (6 and 7) are obtained. In addition, the product Os₃(CO)₁₀(μ-H)(μ-η¹-C₉H₁₀N(CH₃)CN) (8) is obtained, which is the result of an apparent nucleophilic attack of THQ on the coordinated acetonitrile of 1. Thermolysis of 7 yields the dehydrogenation product Os₃(CO)₁₀(μ-H)(μ-η²-C₉H₈N) (10), which maintains the η²-C(8)−N bonding to the metal core, in sharp contrast to 5. Thermolysis of 8 yields Os₃(CO)₈(μ-H)₂(μ₃-η²-C₉H₉N(CH₃)CN) (11) in which the acetonitrile nitrogen caps the trimetallic core and the C−H bond at C(8) has been activated. Reaction of 3 and 6 with CF₃SO₃H or CF₃CO₂H reveals reversible protonation at the nitrogen of the coordinated I or THQ. Protonation of 7 on the other hand takes place at the metal core but 7H⁺ gradually rearranges to 6H⁺ which yields 6 on deprotonation. The solid-state structures of 4, 6, and 10 are reported. In sharp contrast to the above results, isotetrahydroquinoline (ITHQ) reacts with 1 to give the μ-imidoyl cluster Os₃(CO)₁₀(μ-H)(μ-η²-C₉H₈N) (13), which decarbonylates to give the μ₃-imidoyl cluster Os₃(CO)₉(μ-H)(μ₃-η²-C₉H₈N) (14). The thermal behavior and dynamics of these complexes are discussed in the context of current models for hydrodenitrification.